This invention relates to data communications and, in particular, to a device which extends data communications system performance analysis to those systems which may be described as digital systems.
Specifically, digital systems are defined to be those data communication services in which the customer or user has only access to the digital clock and data signals at the communication channel terminations. A typical digital service offering is the Digital Datas System (DDS) offered by American Telephone and Telegraph which is discussed in the following publications: "Digital Data System-Channel Interface Specifications-Addendum" PUB441021A, October, 1981, and "DATAPHONE Digital Service-Preliminary-", PUB441022, September 1974, and "DATAPHONE Switched Digital Service-Channel Interface Specifications-Preliminary-", PUB41023 by the American Telephone and Telegraph Company.
In my commonly assigned U.S. Pat. No. 4,273,955, issued June 16,1981, a network management and control system is described. This system was designed to utilize analog communication media such as telephone channels. The digital data signaling over such channels being accomplished by the use of wireline modems, one modem being located at each analog telephone channel termination. In particular, diagnostic telemetry data was conveyed through the system using the Frequency Division Multiplexing techniques described in my U.S. Pat. No. 4,273,955.
When digital data transmission services are utilized, no excess bandwith is available for diagnostic telemetry transmission and the technique of FDM is not feasable. Some method of time division multiplexing (TDM) must be utilized.
In view of the above, it is the principal object of the present invention to provide a system whereby the monitoring of components of a multilocation digital data communications network may be attained from a central location.
A further object is to provide a system which permits both diagnostic telemetry and test or probe data sequences to be imbedded in user data for transmission over the digital data communication channels.
Other objects and advantages will be apparent from a review of the detailed description of a preferred embodiment of the invention.